...I accidently found out how to make a nomadic race. Here's my files:

https://www.dropbox.com/s/eri06u8bmwx13uz/StarSystemDefs.txt?dl=0 <-- This is an addition for StarSystemDefs in C:/Program Files (86x)/Steam/steamapps/common/Galactic Civilizations 3/data/game

https://www.dropbox.com/s/hk8fj8czf0bebjt/FactionDefs.txt?dl=0  <-- This is an addition to the FactionDefs file, located in the same directory as above. 

And here is some proof:

https://www.dropbox.com/s/qf19558xvssplfh/Galactic%20Civilizations%20III%202.30%207_16_2017%204_29_08%20PM.png?dl=0

I discovered this when I decided that trying to force the Space Monsters into being my slaves didn't work, so I decided taking another go at making a nomadic race. Doing this, I also found out that the space monsters themselves are playable [through console] if the tech tree is replaced. (I'm guessing this is because the fourth tree is basically removed.)

EDIT ah, stumbled around a small problem. Turns out you can survive only one turn like this. Might want to start with a couple scouts and a colony ship. Nevertheless it's a big step forward towards nomadic races and I'm bound to find what causes this problem eventually.

2nd Edit I think I've gotten myself a way to fix it, however, I'm going to need a little bit of help. in data/schema/lib/enums there is a file called PlayerTypes.xsd. I'm off to bed for now, but I would like some help to find what .xml files if any call upon it. I would figure so, since there's a type called Dreadlord, which wasn't an actual faction until the Mega Events DLC, yet the only file that I know of that calls upon it is the FactionsDefs.xsd. If any of you would be so kind as to point me in some sort of direction, I would be very thankful.